Lightning is an important factor that affects the safety of transmission lines and has been the primary reason causing tripping in the line fault for a long time, and it is a natural process of atmospheric activity and has been uncontrollable so far. However, the precautions against lightning can be strengthened by finding the law of lightning strikes through analyzing the frequent accidents. For example, poles and towers in the mountains or peaks, transmission lines near ponds or reservoirs, poles and towers spanning mountains or rivers and lakes, poles and towers and rocky tower footings as well as transmission lines installed with high grounding resistance are the main objects vulnerable to lightning strikes.
Lightning strikes will bring different forms of damage and destruction to the power facilities. Thundercloud discharges will cause lightning overvoltage in the power system. The overvoltage common in overhead lines comprises overvoltage in the transmission lines caused by the lightning strikes near the overhead lines through electromagnetic induction, and overvoltage generated by the direct striking of the lightning on the wires. The overvoltage due to the lightning strikes may cause damage to insulators and transmission lines. The flashover strike of the insulator due to the lightning strikes causes the burnout on porcelain surfaces or the mesh cracks on glass insulators, resulting in a significant reduction of the insulation strength. Lightning strikes on the transmission wires or the lightning conductor may cause broken stand or even breakage, resulting in a failure of the power transmission.
The lightning protection of transmission lines has always been an important part of lightning protection work for the power sector. The lightning disturbance is still one of the important factors affecting the safety of power grids. The impulse flashover, caused by the lightning strikes on the transmission lines, causes the flashover of the insulators in the lines, which then causes a large power-flow current, damages the insulator string and the fitting, resulting in line accidents. In order to protect the transmission lines, the power sector generally installs lightning protectors on the transmission lines.
Arc is free gas with high temperature and high conductivity. Extinguishing the arc is referred to as arc-extinguishing. There are many ways to extinguish arc, most of which use a certain gas or liquid to undertake the main arc-extinguishing work.
The lightning protector is an electrical device capable of releasing lightning or releasing the operation overvoltage energy of the power system to protect the electrical equipment from the damage of transient overvoltage as well as cutting off the freewheeling to avoid the grounded short circuit of the system.
For example, Chinese patent 2015100691235 discloses a countable arc-intercepting lightning protector, including a lightning protector main body and an arc-striking electrode; the arc-striking electrode is fixedly mounted at one end of the main body, the other end of the main body is fixedly mounted, by means of a link fitting, to a crossarm; the main body is provided with an arc-extinguishing path consisting of several arc-extinguishing channels in a repeated Z-shaped arrangement; a copper block is provided at a joint of two adjacent arc-extinguishing channels, and each arc-extinguishing channel is provided with two arc-extinguishing tubes, an arc-guiding ball is provided between the two arc-extinguishing tubes; the arc-extinguishing tube at an inlet of a first arc-extinguishing channel of the arc-extinguishing path is connected to the arc-striking electrode via a threaded arc-guiding rod, the arc-extinguishing tube at an outlet of a last arc-extinguishing channel is connected to a link fitting via a wire; and a counter is provided at the outlet of the last arc-extinguishing channel. The lightning protector extinguishes the arc by using an axial-blast arc-extinguishing method.
Although the patent above has played a very good role in lightning protection, there are still some shortcomings: only a radial blowing arc-extinguishing method is used, the arc is not easy to blow out when it is strong.